The present invention relates generally to the fields of molecular biology and medicine; more particularly to the areas of genetic screening and the identification and treatment of hereditary disorders; and more particularly to identification and treatment of hereditary lymphedema.
The lymphatic system is a complex structure organized in parallel fashion to the circulatory system. In contrast to the circulatory system, which utilizes the heart to pump blood throughout the body, the lymphatic system pumps lymph fluid using the inherent contractility of the lymphatic vessels. The lymphatic vessels are not interconnected in the same manner as the blood vessels, but rather form a set of coordinated structures including the initial lymphatic sinuses [Jeltsch et al., Science, 276:1423-1425 (1997); and Castenholz, A., in Olszewski, W. L. (ed.), Lymph Stasis: Pathophysiology, Diagnosis, and Treatment. CRC Press: Boca Raton, Fla. (1991), pp.15-42] which drain into the lymphatic capillaries and subsequently to the collecting lymphatics which drain into the lymphatic trunks and the thoracic duct which ultimately drains into the venous circulation. The composition of the channels through which lymph passes is varied [Olszewski, W. L., in Olszewski, W. L. (ed), Lymph Stasis: Pathophysiology, Diagnosis, and Treatment. CRC Press: Boca Raton, Fla. (1991), pp. 235-258; and Kinmonth, J. B., in Kinmonth, J. B. (ed), The Lymphatics: Diseases, Lymphography and Surgery. Edward Arnold Publishers: London, England (1972), pp. 82-86], including the single endothelial layers of the initial lymphatics, the multiple layers of the collecting lymphatics including endothelium, muscular and adventitial layers, and the complex organization of the lymph node. The various organs of the body such as skin, lung, and GI tract have components of the lymphatics with various unique features. [See Ohkuma, M., in Olszewski (1991), supra, at pp. 157-190; Uhley, H. and Leeds, S., in Olszewski (1991), supra, at pp. 191-210; and Barrowman, J. A., in Olszewski (1991), at pp. 221-234).] Molecular biology has identified at least a few genes and proteins postulated to have roles mediating the growth and/or embryonic development of the lymphatic system. One such gene/protein is the receptor tyrosine kinase designated Flt4 (fms-like tyrosine kinase 4), cloned from human erythroleukaemia cell and placental cDNA libraries. [See U.S. Pat. No. 5,776,755; Aprelikova et al., Cancer Res., 52: 746-748 (1992); Galland et al., Genomics, 13: 475-478 (1992); Galland et al., Oncogene, 8: 1233-1240 (1993); andPajusola et al., Cancer Res., 52:5738-5743 (1992), all incorporated herein by reference.] Studies showed that, in mouse embryos, a targeted disruption of the Flt4 gene leads to a failure of the remodeling of the primary vascular network, and death after embryonic day 9.5 [Dumont et al., Science, 282: 946-949 (1998)]. These studies suggested that Flt4 has an essential role in the development of the embryonic vasculature, before the emergence of the lymphatic vessels. However, additional studies indicated that, during further development, the expression of Flt4 becomes restricted mainly to lymphatic vessels [Kaipainen, et al., Proc. Natl. Acad Sci. USA, 92: 3566-3570 (1995)].
In humans, there are two isoforms of the Flt4 protein, designated as Flt4s (short, Genbank Accession No. X68203) and Flt4l (long, Genbank Accession Nos. X68203 and S66407, SEQ ID NO: 1). The sequence of these isoforms is largely identical, except for divergence that occurs at the carboxyl terminus of the receptor as a result of alternative MRNA splicing at the 3xe2x80x2 end. The C-terminus of the long form contains three tyrosyl residues, and one of them (Y1337 (SEQ ID NO: 2)) serves as an autophosphorylation site in the receptor [Fournier et al., Oncogene, 11: 921-931 (1995); and Pajusola, et al., Oncogene, 8: 2931-2937 (1993)]. Only the long form is detected in human erythroleukaemia (HEL) and in a megakaryoblastic cell line (the DAMI cells), and the mouse Flt4 gene (Genbank Accession No. L07296) only produces one mRNA transcript, corresponding to Flt4l [Galland et al., Oncogene, 8: 1233-1240 (1993); and Pajusola et al., Cancer Res., 52: 5738-5743 (1992)]. These findings suggest that the long form of Flt4 may be responsible for most of the biological properties of this receptor. The Flt4 protein is glycosylated and proteolytically processed in transfected cells [Pajusola et al., Oncogene, 9: 3545-3555 (1994)]. During this process, the 175 kD form of the receptor matures to a 195 kD form, which is subsequently cleaved into a 125 kD C-terminal fragment, and a 75 kD extracellular domain-containing fragment, which are linked by disulphide bonding in the mature receptor.
Two growth factors, named vascular endothelial growth factors C and D (VEGF-C and VEGF-D) due to amino acid sequence similarity to earlier-discovered vascular endothelial growth factor, have been shown to bind and activate the tyrosine phosphorylation of Flt4. [Achen et al., Proc. Natl. Acad. Sci. USA, 95: 548-553 (1998); Joukov et al, EAfBOJ, 16: 3898-3911; and Joukov et al., EMBO J, 15: 290-298 (1996)]. Because of Flt4xe2x80x2s growth factor binding properties and the fact that Flt4 possesses amino acid sequence similarity to two previously identified VEGF receptors (Fltl/VEGFR-1 and KDR/VEGFR-2), Flt4 has also been designated VEGFR-3, and these terms are used interchangeably herein.
When VEGF-C was intentionally over-expressed under a basal keratin promoter in transgenic mice, a hyperplastic lymphatic vessel network in the skin was observed. [Jeltsch et al., Science, 276:1423-1425 (1997).] The results of this study, when combined with the expression pattern of VEGFR-3 in the lymphatic vasculature, suggest that lymphatic growth may be induced by VEGF-C and mediated via VEGFR-3. Notwithstanding the foregoing insights involving one cell surface receptor and the two apparent ligands therefor, little is known about the developmental regulation of the lymphatic system.
Hereditary or primary lymphedema, first described by Milroy in 1892 [Milroy, N.Y. Med. J, 56:505-508 (1892)], is a developmental disorder of the lymphatic system which leads to a disabling and disfiguring swelling of the extremities. Hereditary lymphedema generally shows an autosomal dominant pattern of inheritance with reduced penetrance, variable expression, and variable age-at-onset [Greenlee et al., Lymphology, 26:156-168 (1993)]. Swelling may appear in one or all limbs, varying in degree and distribution. If untreated, such swelling worsens over time. In rare instances, angiosarcoma may develop in affected tissues [Offori et al., Clin. Exp. Dermatol., 18:174-177 (1993)]. Despite having been described over a century ago, little progress has been made in understanding the mechanisms causing lymphedema. A long-felt need exists for the identification of the presumed genetic variations that underlie hereditary lymphedema, to permit better informed genetic counseling in affected families, earlier diagnosis and treatment, and the development of more targeted and effective lymphedema therapeutic regimens. In addition, identification of genetic markers and high risk members of lymphedema families facilitates the identification and management of environmental factors that influence the expression and severity of a lymnphedema phenotype.
The present invention provides materials and methods that address one or more of the long-felt needs identified above by identifying a genetic marker that correlates and is posited to have a causative role in the development of hereditary lymphedema. The invention is based in part on the discovery that, in several families with members afflicted with hereditary lymphedema, the lymphedema phenotype correlates with genetic markers localized to chromosome 5q34-q35; and that in at least some such families, a missense mutation in the VEGFR-3 gene (which maps to chromosome 5q34-q35) exists that appears to behave in a loss-of-function dominant negative manner to decrease tyrosine kinase signaling of the receptor. In view of the fact that VEGFR-3 acts as a high affinity receptor for vascular endothelial growth factor C (VEGF-C), a growth factor whose effects include modulation of the growth of the lymphatic vascular network, these linkage and biochemical studies provide an important marker for determining a genetic predisposition for lymnphedema in healthy individuals; and for diagnosing hereditary lymphedema in symptomatic individuals. Materials and methods for performing such genetic analyses are considered aspects of the present invention.
Thus, the invention provides genetic screening procedures that entail analyzing a person""s genomexe2x80x94in particular their VEGFR-3 allelesxe2x80x94to determine whether the individual possesses a genetic characteristic found in other individuals that are considered to be afflicted with, or at risk for, developing hereditary lymphedema.
For example, in one embodiment, the invention provides a method for determining a hereditary lymphedema development potential in a human subject comprising the steps of analyzing the coding sequence of the VEGFR-3 genes from the human subject; and determining hereditary lymphedema development potential in said human subject from the analyzing step.
In another embodiment, the invention provides a method of screening a human subject for an increased risk of developing a lymphatic disorder, comprising the steps of: (a) assaying nucleic acid of a human subject to determine a presence or an absence of a mutation altering the encoded VEGFR-3 amino acid sequence or expression of at least one VEGFR-3 allele; and (b) screening for an increased risk of developing a lymphatic disorder from the presence or absence of said mutation.
By xe2x80x9chuman subjectxe2x80x9d is meant any human being, human embryo, or human fetus. It will be apparent that methods of the present invention will be of particular interest to individuals that have themselves been diagnosed with lymphedema or have relatives that have been diagnosed with lymphedema.
By xe2x80x9cscreening for an increased riskxe2x80x9d is meant determination of whether a genetic variation exists in the human subject that correlates with a greater likelihood of developing lymphedema than exists for the human population as a whole, or for a relevant racial or ethnic human sub-population to which the individual belongs. Both positive and negative determinations (i.e., determinations that a genetic predisposition marker is present or is absent) are intended to fall within the scope of screening methods of the invention. In preferred embodiments, the presence of a mutation altering the sequence or expression of at least one Flt4 receptor tyrosine kinase allele in the nucleic acid is correlated with an increased risk of developing a lymphatic disorder, whereas the absence of such a mutation is reported as a negative determination.
By xe2x80x9clymphatic disorderxe2x80x9d is meant any clinical condition affecting the lymphatic system, including but not limited to lymphedemas, lymphangiomas, lymphangiosarcomas, lymphangiomatosis, lymphangiectasis, and cystic hygroma. Preferred embodiments are methods of screening a human subject for an increased risk of developing a lymphedema disorder, i.e., any disorder that physicians would diagnose as lymphedema and that is characterized by swelling associated with lymph accumulation, other than lymphedemas for which non-genetic causes (e.g., parasites, surgery) are known. By way of example, lymphedema disorders include Milroy-Nonne (OMIM 153100) syndrome-early onset lymphedema [Milroy, N.Y Med. J, 56:505-508 (1892); and Dale, J Med. Genet., 22: 274-278 (1985)] and lymphedema praecox (Meige syndrome, OMIM 153200)-late onset lymphedema [Lewis et al., J Ped., 104:641-648 (1984); Holmes et al., Pediatrics 61:575-579 (1978); and Wheeler et al., Plastic Reconstructive Surg, 67:362-364 (1981)] which generally are described as separate entities, both characterized by dominant inheritance. However, there is confusion in the literature about the separation of these disorders. In Milroy""s syndrome, the presence of edema, which is usually more severe in the lower extremities, is seen from birth. Lymphedema praecox presents in a similar fashion but the onset of swelling is usually around puberty. Some cases have been reported to develop in the post-pubertal period. In the particular analyses described herein, the lymphedema families showing linkage to 5q34-q35 show an early onset for most affected individuals, but individuals in these pedigrees have presented during or after puberty.
The xe2x80x9cassayingxe2x80x9d step of the invention may involve any techniques available for analyzing nucleic acid to determine its characteristics, including but not limited to well-known techniques such as single-strand conformation polymorphism analysis (SSCP) [Orita et al., Proc Natl. Acad. Sci. USA, 86: 2766-2770 (1989)]; heteroduplex analysis [White et al., Genomics, 12: 301-306 (1992)]; denaturing gradient gel electrophoresis analysis [Fischer et al., Proc. Natl. Acad. Sci. USA, 80: 1579-1583 (1983); and Riesner et al., Electrophoresis, 10: 377-389 (1989)]; DNA sequencing; RNase cleavage [Myers et al., Science, 230: 1242-1246 (1985)]; chemical cleavage of mismatch techniques [Rowley et al., Genomics, 30: 574-582 (1995); and Roberts et al., Nucl. Acids Res., 25: 3377-3378 (1997)]; restriction fragment length polymorphism analysis; single nucleotide primer extension analysis [Shumaker et al., Hum. Mutat., 7: 346-354 (1996); and Pastinen et al., Genome Res., 7: 606-614 (1997)]; 5xe2x80x2 nuclease assays [Pease et al., Proc. Nati. Acad. Sci. USA, 91:5022-5026 (1994)]; DNA Microchip analysis [Ramsay, G., Nature Biotechnology, 16: 40-48 (p999); and Chee et al., U. S. Pat. No. 5,837,832]; and ligase chain reaction [Whiteley et al., U.S. Pat. No. 5,521,065]. [See generally, Schafer and Hawkins, Nature Biotechnology, 16: 33-39 (1998).] All of the foregoing documents are hereby incorporated by reference in their entirety.
In one preferred embodiment, the assaying involves sequencing of nucleic acid to determine nucleotide sequence thereof, using any available sequencing technique. [See, e.g., Sanger et al., Proc. Natl. Acad. Sci. (USA), 74: 5463-5467 (1977) (dideoxy chain termination method); Mirzabekov, TIBTECH, 12: 27-32 (1994) (sequencing by hybridization); Drmanac et al., Nature Biotechnology, 16: 54-58 (1998); U.S. Pat. No. 5,202,231; and Science, 260: 1649-1652 (1993) (sequencing by hybridization); Kieleczawa et al., Science, 258: 1787-1791 (1992) (sequencing by primer walking); (Douglas et al., Biotechniques, 14: 824-828 (1993) (Direct sequencing of PCR products); and Akane et al., Biotechniques 16: 238-241 (1994); Maxam and Gilbert,Meth. Enzymol., 65: 499-560 (1977) (chemical termination sequencing), all incorporated herein by reference.] The analysis may entail sequencing of the entire VEGFR-3 gene genomic DNA sequence, or portions thereof; or sequencing of the entire VEGFR-3 coding sequence or portions thereof In some circumstances, the analysis may involve a determination of whether an individual possesses a particular VEGFR-3 allelic variant, in which case sequencing of only a small portion of nucleic acidxe2x80x94enough to determine the sequence of a particular codon characterizing the allelic variantxe2x80x94is sufficient. This approach is appropriate, for example, when assaying to determine whether one family member inherited the same allelic variant that has been previously characterized for another family member, or, more generally, whether a person""s genome contains an allelic variant that has been previously characterized and correlated with heritable lymphedema. More generally, the sequencing may be focused on those portions of the VEGFR-3 sequence that encode a VEGFR-3 kinase domain, since several different and apparently causative mutations in affected individuals that have been identified correspond to residues within an intracellular VEGFR-3 kinase domain. Referring to SEQ ID NOs: 1 and 2, the two kinase domains of human wild type VEGFR-3 correspond to nucleotides 2546 to 2848 and 3044 to 3514 of SEQ ID NO: 1, which encode residues 843 to 943 and 1009 to 1165 of SEQ ID NO: 2. Such kinase domains are localized to exons 17-20 and 22-26 in the VEGFR-3 gene, so the sequencing/analysis may be focused on those exons in particular. Molecular modeling suggests that, within these domains, residues G852, G854, G857, K879, E896, H1035, D1037, N1042, D1055, F1056, G1057, E1084, D1096, and RI 159 are of particular importance in comprising or shaping the catalytic pocket of the VEGFR-3 kinase domains, so the sequencing may focus on these residues (in addition to residues described herein for which mutations have already been identified).
In a related embodiment, the invention provides PCR primers useful for amplifying particular exon sequences of human VEGFR-3 genomic DNA. The Examples below identify preferred primers for amplifying Exon 17, Exon 22, and Exon 24 sequences, where specific missense mutations described herein map. In addition, the Examples below describe the Exon-Intron junctions of human VEGFR-3, which, in combination with the VEGFR-3 cDNA sequence provided herein, permit the manufacture of appropriate oligonucleotide primers for other exons. Any such primers of, e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, or more nucleotides that are identical or exactly complementary to a human VEGFR-3 genonuc sequence and that includes or is within 50 nucleotides of a VEGFR-3 exonintron splice site is intended to be within the scope of the invention.
In another embodiment, the assaying step comprises performing a hybridization assay to determine whether nucleic acid from the human subject has a nucleotide sequence identical to or different from one or more reference sequences. In a preferred embodiment, the hybridization involves a determination of whether nucleic acid derived from the human subject will hybridize with one or more oligonucleotides, wherein the oligonucleotides have nucleotide sequences that correspond identically to a portion of the VEGFR-3 gene sequence, preferably the VEGFR-3 coding sequence set forth in SEQ ID NO: 1, or that correspond identically except for one mismatch. The hybridization conditions are selected to differentiate between perfect sequence complementarity and imperfect matches differing by one or more bases. Such hybridization experiments thereby can provide single nucleotide polymorphism sequence information about the nucleic acid from the human subject, by virtue of knowing the sequences of the oligonucleotides used in the experiments.
Several of the techniques outlined above involve an analysis wherein one performs a polynucleotide migration assay, e.g., on a polyacrylamide electrophoresis gel, under denaturing or non-denaturing conditions. Nucleic acid derived from the human subject is subjected to gel electrophoresis, usually adjacent to one or more reference nucleic acids, such as reference VEGFR-3 sequences having a coding sequence identical to all or a portion of SEQ ID NO: 1, or identical except for one known polymorphism. The nucleic acid from the human subject and the reference sequence(s) are subjected to similar chemical or enzymatic treatments and then electrophoresed under conditions whereby the polynucleotides will show a differential migration pattern, unless they contain identical sequences. [See generally Ausubel et al. (eds.), Current Protocols in Molecular Biology, New York: John Wiley and Sons, Inc. (1987-1999); and Sambrook et al, (eds.), Molecular Cloning, A Laboratory Manual, Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press (1989), both incorporated herein by reference in their entirety.] In the context of assaying, the term xe2x80x9cnucleic acid of a human subjectxe2x80x9d is intended to include nucleic acid obtained directly from the human subject (e.g., DNA or RNA obtained from a biological sample such as a blood, tissue, or other cell or fluid sample); and also nucleic acid derived from nucleic acid obtained directly from the human subject. By way of non-limiting examples, well known procedures exist for creating cDNA that is complementary to RNA derived from a biological sample from a human subject, and for amplifying (e.g., via polymerase chain reaction (PCR)) DNA or RNA derived from a biological sample obtained from a human subject. Any such derived polynucleotide which retains relevant nucleotide sequence information of the human subject""s own DNA/RNA is intended to fall within the definition of xe2x80x9cnucleic acid of a human subjectxe2x80x9d for the purposes of the present invention.
In the context of assaying, the term xe2x80x9cmutationxe2x80x9d includes addition, deletion, and/or substitution of one or more nucleotides in the VEGFR-3 gene sequence. The invention is demonstrated by way of non-limiting examples set forth below that identify several mutations in VEGFR-3, including single nucleotide polymorphisms that introduce missense mutations into the VEGFR-3 coding sequence (as compared to the VEGFR-3 cDNA sequence set forth in SEQ ID NO: 1) and other polymorphisms that occur in introns and that are identifiable via sequencing, restriction fragment length polymorphism, or other techniques. Example 2 provides an assay to determine whether a VEGFR-3 mutation inhibits VEGFR-3 signaling. Additional assays to study both ligand binding and signaling activities of VEGFR-3 are disclosed, e.g., in U.S. Pat. No. 5,776,755 and International Patent Publication No. WO 98/33917, published 06 August 1998, both of which are incorporated herein by reference in their entirety. Evidence that a VEGFR-3 mutation inhibits VEGFR-3 signaling is evidence that the mutation may have a causative role in lymphedema phenotype. However, even mutations that have no apparent causative role may serve as useful markers for heritable lymphedema, provided that the appearance of the mutation correlates reliably with the appearance of lymphedema.
In a related embodiment, the invention provides a method of screening for a VEGFR-3 hereditary lymphedema genotype in a human subject, comprising the steps of: (a) providing a biological sample comprising nucleic acid from a human subject; (b) analyzing the nucleic acid for the presence of a mutation or mutations in a VEGFR-3 allele in the nucleic acid of the human subject; (c) determining a VEGFR-3 genotype from said analyzing step; and (d) correlating the presence of a mutation in a VEGFR-3 allele with a hereditary lymphedema genotype. In a preferred embodiment, the biological sample is a cell sample containing human cells that contain genomic DNA of the human subject.
Although more time consuming and expensive than methods involving nucleic acid analysis, the invention also may be practiced by assaying protein of a human subject to determine the presence or absence of an amino acid sequence variation in VEGFR-3 protein from the human subject. Such protein analyses may be performed, e.g., by fragmenting VEGFR-3 protein via chemical or enzymatic methods and sequencing the resultant peptides; or by Western analyses using an antibody having specificity for a particular allelic variant of VEGFR-3.
The invention also provides materials that are useful for performing methods of the invention. For example, the present invention provides oligonucleotides useful as probes in the many analyzing techniques described above. In general, such oligonucleotide probes comprise 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nucleotides that have a sequence that is identical, or exactly complementary, to a portion of a human VEGFR-3 gene sequence, or that is identical or exactly complementary except for one nucleotide substitution. In a preferred embodiment, the oligonucleotides have a sequence that corresponds in the foregoing manner to a human VEGFR-3 coding sequence, and in particular, the VEGFR-3 coding sequence set forth in SEQ ID NO: 1. In one variation, an oligonucleotide probe of the invention is purified and isolated. In another variation, the oligonucleotide probe is labeled, e.g., with a radioisotope, chromophore, or fluorophore. In yet another variation, the probe is covalently attached to a solid support. [See generally Ausubel et al. And Sambrook et al., supra.] In preferred embodiments, the invention comprises an oligonucleotide probe useful for detecting one or more of several mutations that have been characterized herein in affected individuals, including:
(1) a missense mutation at nucleotide 3360 of SEQ ID NO: 1, causing a proline to leucine change at residue 1114 in SEQ ID NO: 2;
(2) a missense mutation at nucleotide 2588 of SEQ ID NO: 1, causing a glycine to arginine change at residue 857 in SEQ ID NO: 2;
(3) a missense mutation at nucleotide 3141 of SEQ ID NO: 1, causing an arginine to proline change at residue 1041 in SEQ ID NO: 2;
(4) a missense mutation at nucleotide 3150 in SEQ ID NO: 1, causing a leucine to proline change at residue 1044 in SEQ ID NO: 2; and
(5) a missense mutation at nucleotide 3164 of SEQ ID NO: 1, causing an aspartic acid to asparagine change at residue 1049 in SEQ ID NO: 2.
For example, the invention provides oligonucleotides comprising anywhere from 6 to 50 nucleotides that have a sequence that is identical to, or exactly complementary to, a portion of the human VEGFR-3 coding sequence set forth in SEQ ID NO: 1, except for a nucleotide substitution corresponding to nucleotide 3360 of SEQ ID NO: 1. Such oligonucleotides may be generically described by the formula XnYZm or its complement; where n and m are integers from 0 to 49; where 5 less than (n+m) less than 49; where Xn is a stretch of n nucleotides identical to a first portion of SEQ ID NO: 1 and Zm is a stretch of m nucleotides identical to a second portion of SEQ ID NO: 1, wherein the first and second portions are separated in SEQ ID NO: 1 by one nucleotide; and wherein Y represents a nucleotide other than the nucleotide that separates the first and second portions of SEQ ID NO: 1. For example, where Xn represents 0 to 49 nlucleotides immediately upstream (5xe2x80x2) of nucleotide 3360 of SEQ ID NO: 1 and Zm represents 0 to 49 nucleotides immediately downstream (3xe2x80x2) of nucleotide 3360 of SEQ ID NO: 1, Y represents a nucleotide other than cytosine, since a cytosine nucleotide is found at position 3360 of SEQ ID NO: 1. In a preferred embodiment, Y is a thymine nucleotide. Similar examples are contemplated for the other specific mutations identified immediately above.
In a related embodiment, the invention provides a kit comprising at least two such oligonucleotide probes. Preferably, the two or more probes are provided in separate containers, or attached to separate solid supports, or attached separately to the same solid support, e.g., on a DNA microchip.
In still another related embodiment, the invention provides an array of oligonucleotide probes immobilized on a solid support, the array having at least 4 probes, preferably at least 100 probes, and preferably up to 100,000, 10,000, or 1000 probes, wherein each probe occupies a separate known site in the array. In a preferred embodiment, the array includes probe sets comprising two to four probes, wherein one probe is exactly identical or exactly complementary to a human VEGFR-3 coding sequence, and the other one to three members of the set are exactly identical to the first member, but for at least one different nucleotide, which different nucleotide is located in the same position in each of the one to three additional set members. In one preferred embodiment, the array comprises several such sets of probes, wherein the sets correspond to different segments of the human VEGFR-3 gene sequence. In a highly preferred embodiment, the array comprises enough sets of oligonucleotides of length N to correspond to every particular N-mer sequence of the VEGFR-3 gene, where N is preferably 6 to 25 and more preferably 9 to 20. Materials and methods for making such probes are known in the art and are described, for example, in U.S. Pat. Nos. 5,837,832, 5,202,231, 5,002,867, and 5,143,854.
Moreover, the discoveries which underlie the present invention identify a target for therapeutic intervention in cases of hereditary lymphedema. The causative mutations in the families that have been studied in greatest detail are mutations that appear to result in VEGFR-3 signaling that is reduced in heterozygous affected individuals, but not completely eliminated. This data supports a therapeutic indication for administration of agents, such as VEGFR-3 ligand polypeptides, that will induce VGFR-3 signaling in the lymphatic endothelia of affected individuals to effect improvement in the structure and function of the lymphatic vasculature of such individuals. In addition, therapeutic gene therapy, to replace defective VEGFR-3 alleles or increase production of VEGFR-3 ligand polypeptides in vivo, is envisioned as an aspect of the invention.
Thus, in yet another aspect, the invention provides a therapeutic or prophylactic method of treatment for lymphedema, comprising the step of administering to a mammalian subject in need of therapeutic or prophylactic treatment for lymphedema a composition comprising a compound effective to induce intracellular signaling of VEGFR-3 in lymphatic endothelial cells that express said receptor. In a preferred embodiment, the compound comprises a polypeptide ligand for VEGFR-3, or a polynucleotide encoding such a ligand, wherein the polynucleotide is administered in a form that results in transcription and translation of the polynucleotide in the mammalian subject to produce the ligand in vivo. In another preferred embodiment, the compound comprises any small molecule that is capable of binding to the VEGFR-3 receptor extracellular or intracellular domain and inducing intracellular signaling.
For example, the invention provides a therapeutic or prophylactic method of treatment for lymphedema, comprising the step of administering to a mammalian subject in need of therapeutic or prophylactic treatment for lymphedema a composition comprising a polynucleotide, the polynucleotide comprising a nucleotide sequence that encodes a vascular endothelial growth factor C (VEGF-C) polypeptide. In a preferred embodiment, the subject is a human subject.
While it is contemplated that the VEGF-C polynucleotide could be administered purely as a prophylactic treatment to prevent lymphedema in subjects at risk for developing lymphedema, it is contemplated in a preferred embodiment that the polynucleotide be administered to subjects afflicted with lymphedema, for the purpose of ameliorating its symptoms (e.g., swelling due to the accumulation of lymph). The polynucleotide is included in the composition in an amount and in a form effective to promote expression of a VEGF-C polypeptide in or near the lymphatic endothelia of the mammalian subject, to stimulate VEGFR-3 signaling in the lymphatic endothelia of the subject.
In a preferred embodiment, the mammalian subject is a human subject. Practice of methods of the invention in other mammalian subjects, especially mammals that are conventionally used as models for demonstrating therapeutic efficacy in humans (e.g., primate, porcine, canine, equine, murine, or rabbit animals), also is contemplated. Several potential animal models for hereditary lymphedema have been described in the literature. [See, e.g., Lyon et al., Mouse News Lett. 71: 26 (1984), Mouse News Lett. 74: 96 (1986), and Genetic variants and strains of the laboratory mouse, 2nd ed., New York: Oxford University Press (1989), p. 70 (Chylous ascites mouse); Dumont et al., Science, 282: 946-949 (1998) (heterozygous VEGFR-3 knockout mouse); Patterson et al., xe2x80x9cHereditary Lymphedema,xe2x80x9d Comparative Pathology Bulletin, 3: 2 (1971) (canine hereditary lymphedema model); van der Putte, xe2x80x9cCongenital Hereditary Lymphedema in the Pig,xe2x80x9d Lympho, 11: 1-9 (1978); and Campbell-Beggs et al., xe2x80x9cChyloabdomen in a neonatal foal,xe2x80x9d Veterinary Record, 137: 96-98 (1995).] Those models which are determined to have analogous mutations to the VEGFR-3 gene, such as the Chylous ascetei (Chy) mouse, are preferred. The present inventors have analyzed the VEGFR-3 genes of the Chy mouse and determined that affected mice contain a missense mutation that results in a phenylalanine (rather than an isoleucine) in the VEGFR-3 sequence at a position corresponding to the isoleucine at position 1053 of SEQ ID NO: 2. This mutation maps to the catalytic pocket region of the tyrosine kinase domain of the VEGFR-3 protein, and may represent a viable model for identical mutations in human (if discovered) or other mutations in humans that similarly affect the tyrosine kinase catalytic domain. The Chy mouse has peripheral swelling (oedema) after birth and chyle ascites. In another embodiment, xe2x80x9cknock inxe2x80x9d homologous recombination genetic engineering strategies are used to create an animal model (e.g., a mouse model) having a VEGFR-3 allelic variation analogous to the human variations described herein. [See, e.g., Partanen et al., Genes and Development, 12: 2332-2344 (1998) (gene targeting to introduce mutations into a receptor protein (FGFR-1) in mice).] Such mice can also be bread to the heterozygous VEGFR-3 knockout mice or Chy mice described above to further modify the phenotypic severity of the lymphedema disease.
For the practice of methods of the invention, the term xe2x80x9cVEGF-C polypeptidexe2x80x9d is intended to include any polypeptide that has a VEGF-C or VEGF-C analog amino acid sequence (as defined elsewhere herein in greater detail) and that is able to bind the VEGFR-3 extracellular domain and stimulate VEGFR-3 signaling in vivo. The term xe2x80x9cVEGF-C polynucleotidexe2x80x9d is intended to include any polynucleotide (e.g., DNA or RNA, single- or double-stranded) comprising a nucleotide sequence that encodes a VEGF-C polypeptide. Due to the well-known degeneracy of the genetic code, multiple VEGF-C polynucleotide sequences exist that encode any selected VEGF-C polypeptide. Preferred VEGF-C polynucleotides, polypeptides, and VEGF-C variants and analogs for use in this invention are disclosed in International Patent Application No. PCT/US98/01973, published as WO 98/33917, incorporated herein by reference in its entirety.
For treatment of humans, VEGF-C polypeptides with an amino acid sequence of a human VEGF-C are highly preferred, and polynucleotides comprising a nucleotide sequence of a human VEGF-C cDNA are highly preferred. By xe2x80x9chuman VEGF-Cxe2x80x9d is meant a polypeptide corresponding to a naturally occurring protein (prepro-protein, partially-processed protein, or fully-processed mature protein) encoded by any allele of the human VEGF-C gene, or a polypeptide comprising a biologically active fragment of a naturally-occurring mature protein. By way of example, a human VEGF-C comprises a continuous portion of the amino acid sequence set forth in SEQ ID NO: 4 sufficient to permit the polypeptide to bind and stimulate VEGFR-3 phosphorylation in cells that express such receptors. A polypeptide comprising amino acids 131-211 of SEQ ID NO: 4 is specifically contemplated. For example, polypeptides having an amino acid sequence comprising a continuous portion of SEQ ID NO: 4, the continuous portion having, as its amino terminus, an amino acid selected from the group consisting of positions 30-131 of SEQ ID NO: 4, and having, as its carboxyl terminus, an amino acid selected from the group consisting of positions 211-419 of SEQ ID NO: 4 are contemplated. An amino terminus selected from the group consisting of positions 102-131 of SEQ ID NO: 4 is preferred, and an amino terminus selected from the group consisting of positions 103-113 of SEQ ID NO: 4 is highly preferred. Likewise, a carboxyl terminus selected fi-om the group consisting of positions 211-227 of SEQ ID NO: 4 is preferred. As stated above, the term xe2x80x9chuman VEGF-Cxe2x80x9d also is intended to encompass polypeptides encoded by allelic variants of the human VEGF-C characterized by the sequences set forth in SEQ ID NOs: 3 and 4.
Moreover, since the therapeutic VEGF-C is to be administered as recombinant VEGF-C or indirectly via somatic gene therapy, it is within the skill in the art to make and use analogs of human VEGF-C (and polynucleotides that encode such analogs) wherein one or more amino acids have been added, deleted, or replaced with other amino acids, especially with conservative replacements, and wherein the VEGFR-3-stimulatory biological activity has been retained. Analogs that retain VEGFR-3-stimulatory VEGF-C biological activity are contemplated as VEGF-C polypeptides for use in the present invention. In a preferred embodiment, analogs having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 such modifications and that retain VEGFR-3-stimulatory VEGF-C biological activity are contemplated as VEGF-C polypeptides for use in the present invention. !nalogs having a deletion of or substitution for the cysteine residue at position 156 of SEQ ID NO: 4 and that retain VEGFR-3 stimulatory activity but have reduced activity toward the receptor VEGFR-2, which is expressed in blood vessels, are specifically contemplated. See WO 98/33917. Polynucleotides encoding such analogs are generated using conventional PCR, site-directed mutagenesis, and chemical synthesis techniques.
Also contemplated as VEGF-C polypeptides are non-human mammalian or avian VEGF-C polypeptides and polynucleotides. By xe2x80x9cmammalian VEGF-Cxe2x80x9d is meant a polypeptide corresponding to a naturally occurring protein (prepro-protein, partially-processed protein, or fully-processed mature protein) encoded by any allele of a VEGF-C gene of any mammal, or a polypeptide comprising a biologically active fragment of a mature protein. The term xe2x80x9cmammalian VEGF-C polypeptidexe2x80x9d is intended to include analogs of mammalian VEGF-C""s that possess the in vivo VEGFR-3-stimulatory effects of the mammalian VEGF-C.
Irrespective of which encoded VEGF-C polypeptide is chosen, any VEGF-C polynucleotide gene therapy pharmaceutical encoding it preferably comprises a nucleotide sequence encoding a secretory signal peptide fused in-frame with the VEGF-C polypeptide sequence. The secretory signal peptide directs secretion of the VEGF-C polypeptide by the cells that express the polynucleotide, and is cleaved by the cell from the secreted VEGF-C polypeptide. For example, the VEGF-C polynucleotide could encode the complete prepro-VEGF-C sequence set forth in SEQ ED NO: 4; or could encode the VEGF-C signal peptide fused in-frame to a sequence encoding a fully-processed VEGF-C (e.g., amino acids 103-227 of SEQ ID NO: 4) or VEGF-C analog. Moreover, there is no requirement that the signal peptide be derived from VEGF-C. The signal peptide sequence can be that of another secreted protein, or can be a completely synthetic signal sequence effective to direct secretion in cells of the mammalian subject.
In one embodiment, the VEGF-C polynucleotide of the invention comprises a nucleotide sequence that will hybridize to a polynucleotide that is complementary to the human VEGF-C CDNA sequence specified in SEQ ID NO: 3 under the following exemplary stringent hybridization conditions: hybridization at 42xc2x0 C. in 50% formamide, 5xc3x97SSC, 20 mM Naxc2x7PO4, pH 6.8; and washing in IX SSC at 55xc2x0 C. for 30 minutes; and wherein the nucleotide sequence encodes a polypeptide that binds and stimulates human VEGFR-3. It is understood that variation in these exemplary conditions occur based on the length and GC nucleotide content of the sequences to be hybridized. Formulas standard in the art are appropriate for determining appropriate hybridization conditions. [See Sambrook et al., Molecular Cloning: A Laboratory Manual (Second ed., Cold Spring Harbor, N.Y. : Cold Spring Harbor Laboratory Press, 1989) xc2xa7xc2xa7 9.47-9.51.] In preferred embodiments, the VEGF-C polynucleotide further comprises additional sequences to facilitate the VEGF-C gene therapy. In one embodiment, a xe2x80x9cnakedxe2x80x9d VEGF-C transgene (i.e., a transgene without a viral, liposomal, or other vector to facilitate transfection) is employed for gene therapy. In this embodiment, the VEGF-C polynucleotide preferably comprises a suitable promoter and/or enhancer sequence (e.g., cytomegalovirus promoter/enhancer [Lehner et al., J Clin. Microbiol., 29:2494-2502 (1991); Boshart etal., Cell, 41:521-530 (1985)]; Rous sarcoma virus promoter [Davis et al., Hum. Gene Ther., 4:151 (1993)]; Tie promoter [Korhonen et al., Blood, 86(5): 1828-1835 (1995)]; or simian virus 40 promoter) for expression in the target mammalian cells, the promoter being operatively linked upstream (i.e., 5xe2x80x2) of the VEGF-C coding sequence. The VEGF-C polynucleotide also preferably further includes a suitable polyadenylation sequence (,e.g., the SV40 or human growth hormone gene polyadenylation sequence) operably linked downstream (i.e., 3xe2x80x2) of the VEGF-C coding sequence. The polynucleotide may fairther optionally comprise sequences whose only intended function is to facilitate large-scale production of the vector, e.g., in bacteria, such as a bacterial origin of replication and a sequence encoding a selectable marker. However, in a preferred embodiment, such extraneous sequences are at least partially cleaved off prior to administration to humans according to methods of the invention. One can manufacture and administer such polynucleotides to achieve successful gene therapy using procedures that have been described in the literature for other transgenes. See, e.g., Isner et al., Circulation, 91: 2687-2692 (1995); and Isner et al., Human Gene Therapy, 7: 989-1011 (1996); incorporated herein by reference in the entirety.
Any suitable vector may be used to introduce the VEGF-C transgene into the host. Exemplary vectors that have been described in the literature include replication-deficient retroviral vectors, including but not limited to lentivirus vectors []Kim et al, J Virol., 72(l): 811-816 (1998); Kingsman and Johnson, Scrip Magazine, October, 1998, pp. 43-46.]; adeno-associated viral vectors [Gnatenko et al., J. Livestig. Med., 45: 87-98 (1997)]; adenoviral vectors [See, e.g., U.S. Pat. No. 5,792,453; Quantin et al., Proc. Natl. Acad. Sci. USA, 89: 2581-2584 (1992); Stratford-Perricadet et al., J. Clin. Invest., 90: 626-630 (1992); and Rosenfeld et al., Cell, 68: 143-155 (1992)]; Lipofectin-mediated gene transfer (BRL); liposomal vectors [See, e.g., U.S. Pat. No. 5,631,237 (Liposomes comprising Sendai virus proteins)]; and combinations thereof All of the foregoing documents are incorporated herein by reference in the entirety. Replication-deficient adenoviral vectors constitute a preferred embodiment.
In embodiments employing a viral vector, preferred polynucleotides still include a suitable promoter and polyadenylation sequence as described above. Moreover, it will be readily apparent that, in these embodiments, the polynucleotide further includes vector polynucleotide sequences (e.g., adenoviral polynucleotide sequences) operably connected to the sequence encoding a VEGF-C polypeptide.
Thus, in one embodiment the composition to be administered comprises a, vector, wherein the vector comprises the VEGF-C polynucleotide. In a preferred embodiment, the vector is an adenovirus vector. In a highly preferred embodiment, the adenovirus vector is replication-deficient, i.e., it cannot replicate in the mammalian subject due to deletion of essential viral-replication sequences from the adenoviral genome. For example, the inventors contemplate a method wherein the vector comprises a replication-deficient adenovirus, the adenovirus comprising the VEGF-C polynucleotide operably connected to a promoter and flanked on either end by adenoviral polynucleotide sequences.
The composition to be administered according to methods of the invention preferably comprises (in addition to the polynucleotide or vector) a pharmaceutically-acceptable carrier solution such as water, saline, phosphate-buffered saline, glucose, or other carriers conventionally used to deliver therapeutics intravascularly. Multi-gene therapy is also contemplated, in which case the composition optionally comprises both the VEGF-C polynucleotide/vector and another polynucleotide/vector. As described in greater detail below, a VEGF-D transgene is a preferred candidate for co-administration with the VEGF-C transgene.
The xe2x80x9cadministeringxe2x80x9d that is performed according to the present method may be performed using any medically-accepted means for introducing a therapeutic directly or indirectly into a mammalian subject to reach the lymph or the lymphatic system, including but not limited to injections; oral ingestion; intranasal or topical administration; and the like. In a preferred embodiment, administration of the composition comprising the VEGF-C polynucleotide is performed intravascularly, such as by intravenous or intra-arterial injection, or by subcutaneous injection or local depot administration. In a highly preferred embodiment, the composition is administered locally, e.g., to the site of swelling.
In still another variation, endothelial cells or endothelial progenitor cells are transfected ex vivo with a wild type VEGFR-3 transgene, and the transfected cells are administered to the mammalian subject.
In another aspect, the invention provides a therapeutic or prophylactic method of treating for lymphedema, comprising the step of administering to a mammalian subject in need of treatment for lymphedema a composition comprising a VEGF-C polypeptide, in an amount effective to treat or prevent swelling associated with lymphedema. Administration via one or more intravenous or subcutaneous injections is contemplated. Co-administration of VEGF-C polynucleotides and VEGF-C polypeptides is also contemplated.
In yet another embodiment, the invention provides the use of a VEGF-C polynucleotide or VEGF-C polypeptide for the manufacture of a medicament for the treatment or prevention of lymphedema.
In still another embodiment, the invention provides a therapeutic or prophylactic method of treatment for lymphedema, comprising the step of administering to a mammalian subject in need of therapeutic or prophylactic treatment of lymphedema a composition comprising a polynucleotide, the polynucleotide comprising a nucleotide sequence that encodes a vascular endothelial growth factor D (VEGF-D) polypeptide. Such methods are practiced essentially as described herein with respect to VEGF-C-encoding polynucleotides, except that polynucleotides encoding VEGF-D are employed. A detailed description of the human VEGF-D gene and protein are provided in Achen, et al., Proc. Nat""l Acad. Sci. US.A., 95(2): 548-553 (1998); International Patent Publication No. WO 98/07832, published 26 February 1998; and in Genbank Accession No. AJ000185, all incorporated herein by reference. A cDNA and deduced amino acid sequence for prepro-VEGF-D is set forth herein in SEQ ID NOs: 5 and 6. Of course, due to the well-known degeneracy of the genetic code, multiple VEGF-D encoding polynucleotide sequence exist, any of which may be employed according to the methods taught herein.
As described herein in detail with respect to VEGF-C, the use of polynucleotides that encode VEGF-D fragments, VEGF-D analogs, VEGF-D allelic and interspecies variants, and the like which possess in vivo stimulatory effects of human VEGF-D are all contemplated as being encompassed by the present invention.
In yet another embodiment, the invention provides a therapeutic or prophylactic method of treatment for lymphedema, comprising the step of administering to a mammalian subject in need of treatment for lymphedema a composition comprising a VEGF-D polypeptide, in an amount effective to treat or prevent swelling associated with lymphedema. Administration via one or more intravenous or subcutaneous injections is contemplated.
The VEGFR-3 allelic variant polynucleotides and polypeptides described herein that were discovered and characterized by the present inventors are themselves considered aspects of the invention. Such polynucleotides and polypeptides are useful, for example, in screening assays (e.g., cell-based assays or assays involving transgenic mice that express the polynucleotide in lieu of a native WGF-3 allele) to study the biological activities of VEGFR-3 variant alleles and identify compounds that are capable of modulating that activity, e.g., to identify therapeutic candidates for treatment of lymphedema. Such screening assays are also considered aspects of the invention.
The polypeptides of the invention are intended to include complete AEGFR-3 polypeptides with signal peptide (e.g., approximately residues 1 to 20 of SEQ ID NO: 2), mature VEGFR-3 polypeptides lacking any signal peptide, and recombinant variants wherein a foreign or synthetic signal peptide has been fused to the mature VEGFR-3 polypeptide. Polynucleotides of the invention include all polynucleotides that encode all such polypeptides. It will be understood that for essentially any polypeptide, many polynucleotides can be constructed that encode the polypeptide by virtue of the well known degeneracy of the genetic code. All such polynucleotides are intended as aspects of the invention.
Thus, in yet another aspect, the invention provides a purified polynucleotide comprising a nucleotide sequence encoding a human VEGFR-3 protein variant, wherein said polynucleotide is capable of hybridizing to the complement of SEQ ID NO: 1 under stringent hybridization conditions, and wherein the encoded VEGFR-3 protein variant has an amino acid sequence that differs at position 1114, 857, 1041, 1044 or 1049 from the amino acid sequence set forth in SEQ ID NO: 1. Exemplary conditions are as follows: hybridization at 42xc2x0 C. in 50% formamide, 5xc3x97SSC, 20 mM Na-PO4, pH 6.8; and washing in 0.2xc3x97SSC at 55xc2x0 C. It is understood by those of skill in the art that variation in these conditions occurs based on the length and CrC nucleotide content of the sequences to be hybridized. Formulas standard in the art are appropriate for determining appropriate hybridization conditions. [See Sambrook et al. (1989), supra, xc2xa7xc2xa7 9.47-9.51.]
In a related embodiment, the invention provides a purified polynucleotide comprising a nucleotide sequence encoding a VEGFR-3 protein of a human that is affected with heritable lymphedema or other lymphatic disorder; wherein the polynucleotide is capable of hybridizing to the complement of SEQ ID NO: 1 under stringent hybridization conditions, and wherein the encoded polynucleotide has an amino acid sequence that differs from SEQ ID NO: 1 at at least one codon. It will be understood that conventional recombinant techniques can be used to isolate such polynucleotides from individuals affected with heritable lymphedema or their relatives. The wildtype VEGFR-3 cDNA sequence set forth in SEQ ID NO: 1 (or its complement, or fragments thereof) is used as a probe to identify and isolate VEGFR-3 sequences from nucleic acid derived from the individuals. Alternatively, PCR amplification primers based on the wildtype VEGFR-3 sequence are generated and used to amplify either VEGFR-3 genomic DNA or VEGFR-3 MRNA from the human suibject. The resultant amplified genomic DNA or cDNA is sequenced to determine the variations that characterize the VEGFR-3 lymphedema allele of the individual. Preferred VEGFR-3 lymphedema alleles include, but are not limited to the P 1114L, Cr857R, R1041P, L1044P and D1049N alleles described in detail herein.
In addition, the invention provides vectors that comprise the polynucleotides of the invention. Such vectors are useful for amplifying and expressing the VEGFR-3 proteins encoded by the polynucleotides, and for creating recombinant host cells and/or transgenic animals that express the polynucleotides. The invention further provides a host cell transformed or transfected with polynucleotides (including vectors) of the invention. In a preferred embodiment, the host cell expresses the encoded VEGFR-3 protein on its surface. Such host cells are useful in cell-based screening assays for identifying modulators that stimulate or inhibit signaling of the encoded VEGFR-3. Modulators that stimulate VEGFR-3 signaling have utility as therapeutics to treat lymphedemas, whereas modulators that are inhibitory have utility for treating hyperplastic lymphatic conditions mediated by the allelic variant VEGFR-3. In a preferred embodiment, host cells of the invention are co-transfected with both a wildtype and an allelic variant VEGFR-3 polynucleotide, such that the cells express both receptor types on their surface. Such host cells are preferred for simulating a heterozygous VEGFR-3 genotype of many individuals affected with lymphedema.
In yet another aspect, the invention provides a transgenic mammal, e.g., mouse, characterized by a non-native VEGFR-3 allele that has been introduced into the mouse, and the transgenic progeny thereof Preferred allelic variants include allelic variants that correlate with hereditary lymphedema in human subjects, such as an allelic variant wherein a P11 14L, G857R, R1041P, L1044P or D1049N missense mutation has been introduced into the murine VEGFR-3 gene, or wherein the human P 11 14L, .G857R, R1041P, L1044P or D1049N allelic variant has been substituted for a murine VEGFR-3 allele. Such mice are produced using standard methods. [See, e.g., Hogan et al (eds.), Manipulating the Mouse Embryo, Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory (1986).] The introduction of the human-like mutations into non-human sequences is readily achieved with standard techniques, such as site-directed mutagenesis. The determination of which residues in a non-human sequence to alter to mimic the foregoing human mutations is routine since the foregoing mutations all occur in regions of the VEGFR-3 sequence that contain residues that are highly conserved between species. See FIGS. 3A-3B.
In yet another aspect, the invention provides assays for identifying modulators of VEGFR-3 signaling, particularly modulators of the signaling of allelic variants of VEGFR-3 that correlate with lymphatic disorders such as heritable lymphedema. For example, the invention provides a method for identifying a modulator of intracellular VEGFR-3 signaling, comprising the steps of: contacting a cell expressing at least one mutant mammalian VEGFR-3 polypeptide in the presence and in the absence of a putative modulator compound; b) detecting VEGFR-3 signaling in the cell; and c) identifying a putative modulator compound in view of decreased or increased signaling in the presence of the putative modulator, as compared to signaling in the absence of the putative modulator.
By xe2x80x9cmutant mammalian VEGFR-3 polypeptidexe2x80x9d is meant a VEGFR-3 polypeptide that varies from a wildtype mammalian VEGFR-3 polypeptide (e.g., by virtue of one or more amino acid additions, deletions, or substitutions), wherein the variation is reflective of a naturally occurring variation that has been correlated with a lymphatic disorder, such as lymphedema. By way of example, the previously described substitution variations of human VEGFR-3, such as P 1114L, have been correlated with heritable lymphedema, Any of the human allelic variants described above, or analogous human allelic variants having a different substitution at the indicated amino acid positions, or a non-human VEGFR-3 into which a mutation at the position corresponding to any of the described positions has been introduced are all examples of mutant mammalian VEGFR-3 polypeptides.
The detecting step can entail the detection of any parameter indicative of VEGFR-3 signaling. For example, the detecting step can entail a measurement of VEGFR-3 autophosphorylation, or a measurement of VEGFR-3-mediated cell growth, or a measurement of any step in the VEGFR-3 signaling cascade between VEGFR-3 aatophosphorylation and cell growth.
In a preferred embodiment, the method is practiced with a cell that expresses the mutant mammalian VEGFR-3 polypeptide and a wildtype mammalian VEGFR-3 polypeptide. Such cells are thought to better mimic the conditions in haterozygous individuals suffering from a VEGFR-3-mediated lymphatic disorder. In a highly preferred embodiment, the mutant and wildtype VEGFR-3 polypeptides are human. In the preferred embodiments, the mutant VEGFR-3 polypeptide comprises a leucine amino acid at the position corresponding to position 1114 of SEQ ID NO: 2; an arginine at the position corresponding to position 857 of SEQ ID NO: 2; a proline amino acid at the position corresponding to position 1041 of SEQ ID NO: 2; a proline amino acid at the position corresponding to position 1044 of SEQ ID NO: 2; or an asparagine at the position corresponding to position 1049 of SEQ ID NO: 2.
Additional features and variations of the invention will be apparent to those skilled in the art from the entirety of this application, including the drawing and detailed description, and all such features are intended as aspects of the invention. Likewise, features of the invention described herein can be re-combined into additional embodiments that are also intended as aspects of the invention, irrespective of whether the combination of features is specifically mentioned above as an aspect or embodiment of the invention. Also, only such limitations which are described herein as critical to the invention should be viewed as such; variations of the invention lacking limitations which have not been described herein as critical are intended as aspects of the invention.
In addition to the foregoing, the invention includes, as an additional aspect, all embodiments of the invention narrower in scope in any way than the variations specifically mentioned above. Although the applicant(s) invented the full scope of the claims appended hereto, the claims appended hereto are not intended to encompass within their scope the prior art work of others. Therefore, in the event that statutory prior art within the scope of a claim is brought to the attention of the applicants by a Patent Office or other entity or individual, the applicant(s) reserve the right to exercise amendment rights under applicable patent laws to redefine the subject matter of such a claim to specifically exclude such statutory prior art or obvious variations of statutory prior art from the scope of such a claim. Variations of the invention defined by such amended claims also are intended as aspects of the invention.